Well without a permanent setup, I think that rules out HTC Vive and Oculus Rift. I'd say get some Google Daydreams, some Cardboard (good ones such as the Merge VR), AND some GearVRs. Let people supply their own phone for 1 charge, OR you can supply the phone (set on WiFi) for an upcharge. Get some older BUT compatible Samsung phones, and some pixel phones. OR get a permanent location and PC with HTC Vive and Oculus!